The present invention is related to earthworking implements and more particularly to an automatic control for positioning the bucket on the outer end of a boom that is pivotally supported on a vehicle.
Earthworking implements, commonly referred to as front end loaders, have been in existence for many years. These units consist of a vehicle that has a pair of lift arms defining a boom pivoted thereon with a material handling implement pivoted on the outer end of the boom. The pivotal movement of both the boom and material handling unit is controlled by fluid rams.
One of the problems encountered with loaders of this type is the danger in having the material handling unit tilt towards the vehicle during the elevation of the boom and consequently the possibility of spilling the contents onto the operator is a serious hazard. Numerous solutions to this problem have been proposed. Prior attempts to solve this problem included self-leveling means in the form of a linkage between the lift arms and the booms. While various types of linkages have been suggested for solving this problem, linkages have a serious shortcoming in that there is no way in which the effect of the linkage can be manually interrupted.
To overcome this shortcoming, various types of hydraulic self-leveling systems have been proposed. For example, one type of system incorporates additional slave fluid rams which are connected to the bucket tilt fluid rams to automatically supply fluid during the raising and lowering operation. These slave fluid rams are interposed between the vehicle and the boom. Again, no provision is made for interrupting the leveling function by the operator.
In more recent years, other types of hydraulic leveling systems have been proposed. These systems normally include a single complicated valve housing which incorporates the valves for operating the boom rams and bucket rams as well as an interconnection between the two to produce the leveling function. Again, such units do not normally include provisions for allowing the operator to interrupt the leveling function, when desired.